Abstract
Choosing to perform mitral valve (MV) repair or replacement remains a
hot and highly debated topic. The current guidelines seem to be
conflicting in this specific field and the evidences at our disposal are
scarce, only one small randomized trial and few larger retrospective
studies. The meta-analysis by Gamal and coworkers tries to summarize the
current evidences, concluding that MV replacement for the treatment of
ischemic mitral regurgitation is at least as safe as repair and
certainly offers a more stable result over time than the latter.
Obviously, the implantation of a prosthesis, especially a mechanical
one, brings with it a series of problems, such as anticoagulation and,
above all, a possible lack of ventricular remodeling, especially if a
chordal sparing replacement is not performed.
It must be said, on the other hand, that isolated annuloplasty cannot
act as a counterpart to replacement, because ischemic MR cannot be
considered only an annular disease. Therefore, wanting to mimic the
nature that, after an infarction, enacts a series of changes involving
also the mitral leaflets and chordae, the surgeons are called to act
also on these two entities and not only to downsize the annulus.
In a nutshell, a procedure should not be opposed in a fundamentalist way
to another one, but we must accept the concept of armamentarium where
both procedures are present and tail on the single patient, and also on
the surgeon’s expertise, the technique guaranteeing the best possible
result.
Ennio Flaiano, an important Italian writer said “I have few ideas but
confused” and we strongly believe that it is really appropriate to make
this quote talking about the treatment of ischemic mitral regurgitation.
Indeed, comparing the two most important guidelines on the management of
heart valve disease, the European [1] and the North American [2]
ones, it is possible to read two different recommendations. The former
states that although the surgical approach has to be tailored to the
individual case, in selected patients without advanced left ventricular
(LV) remodeling, mitral valve repair with an undersized complete rigid
ring restores valve competence, improves symptoms, and results in
reverse LV remodeling. Conversely, even if valve replacement avoids
recurrence of mitral regurgitation, this does not translate into better
LV reverse [3] From this it is possible to infer that they lean
toward a conservative procedure over MV replacement.
The AHA/ACC guidelines [2], on the other hand, unequivocally
recommend mitral replacement with chordal sparing over annuloplasty,
with a 2b class of evidence[3-5].
So apparently choosing or not choosing one procedure rather the other
has become a geographical issue.
In this confusing scenario, the meta-analysis of Gamal and coworkers
[6] tries to thin out at least somewhat the fog. Among 2987 records
initially identified, the authors report pooled results of 14 studies
including only one randomized trial [7]. Pooled analysis on
mortality clearly confirms that MV replacement is as safe as MV repair
[OR (95 % CI): 0.66 (0.41-1.07)], as already reported in both
clinical trial and some large retrospective analyses, already cited by
AHA/ACC guidelines [2-5,7].
Likewise, MV repair is confirmed to be a harbinger of a higher rate of
late MR recurrence (pooled rate [200 (34.4 %) vs 22 (3.9 %); OR
(16.8 (5.07-55.7, p=0.00001) although this is not matched by a
significant increase in the rate of reinterventions [55 (7.0 %) and
40 (6.0 %); OR (95 % CI): 1.34 (0.87-2.06), p=0.19]. This difference
can obviously be explained by the fact that MR recurrence includes by
definition also moderate grade that is not indicated for surgery in the
first instance, let alone as reintervention, and by the fact that
patients who have undergone surgery often refuse to undergo a new
procedure and choose the path of medical therapy.
Conversely, repair seems to result in improved left ventricular
remodeling with consequent improvement in the patient’s functional
capacity.
However, the latter finding could be related to the fact that not
everyone performs mitral replacement with sparing of the subvalvular
apparatus as suggested by many surgeons[8] .
Indeed, in CTSNET trial [7], where 95.4% of those receiving valve
replacement had also a chordal-sparing procedure, the mean change of
left ventricular end systolic volume from baseline was −9.0
ml/m2 and −6.5 / m2), not
statistically significant (p=0.19),
Similarly, in a large multicenter Italian study [5] in which almost
all the patients had MV replacement with preservation of
valvular-subvalvular continuity, LV remodeling in terms of ejection
fraction was similar in both groups (P =0.66).
From what has just been said, it would seem that the best choice is to
replace the mitral valve, in the presence of ischemic etiology, because
at equal survival, repair results in a higher recurrence rate. Yet, as
we have seen, the European guidelines continue to support the choice of
repair as a priority without consistent scientific evidences (rather,
the opposite).
To best address the issue of high MR recurrence rate, we must return for
a moment to the definition of secondary (or ischemic, predominantly)
mitral insufficiency and change the paradigm of surgical treatment of
this disease. In a recent editorial [9], we have already pointed out
that ischemic MR represents a unique situation in cardiac surgery. In
fact, although MR has long been considered a ventricular problem,
suggesting that the valve leaflets and chordal structures are merely
innocent bystanders, this concept needs to be challenged.
In ischemic MR, a set of adaptive processes termed ‘mitral plasticity’
takes the field aimed to reduce the amount of regurgitation.
Unfortunately, the mitral plasticity is not always able to achieve the
goal of balancing higher tenting forces and papillary muscles
displacement.
Mimicking what the nature does, surgery may adopt some surgical steps to
go along with the annuloplasty, such as anterior leaflet augmentation
and second order chordal cutting [10].
We believe it is time to end this feud between repair and replacement
(figure 1). It is now obvious that they are both worthwhile surgical
approaches, and this is also confirmed by the meta-analysis by Gamal et
al [6].
Already at the beginning of the 2000s we proposed a simple
echocardiographic parameter, the coaptation depth, to choose between the
two techniques, reserving replacement for patients with worse LV
remodeling, going against the dogma according to which MV repair should
be the predominant choice to be adopted [11]. Today we know that
isolated annuloplasty may not be enough to reach a long-term stability
and competence of the valve and, in these cases, we can choose between a
more complex MV repair procedure that includes also a valvular and
subvalvular procedure, or valve replacement. In a nutshell, as often
happens in surgery, a procedure should not be opposed in a
fundamentalist way to another one, but we must accept the concept of
armamentarium where both procedures are present and tail on the single
patient, and also on the surgeon’s expertise, the technique guaranteeing
the best possible result. But the struggle to generate a single,
long-lasting, and effective technique in ischemic mitral regurgitation
will certainly continue….at least, in the guidelines
recommendations.